1. Field of the Invention
The present invention relates to an improvement in a fluid coking process.
2. Description of the Prior Art
Fluid coking is a well-known process. See, for example, U.S. Pat. No. 2,881,130, the teachings of which are hereby incorporated by reference. Integrated fluid coking and coke gasification processes are also known and disclosed, for example, in U.S. Pat. Nos. 3,702,516; 3,759,676, and 4,325,815, the teachings of which are hereby incorporated by reference.
In the fluid coking process or in the integrated fluid coking and coke gasification processes, the solids present in the coking reactor have adherent hydrocarbons. The solids may be inert solids, catalytic solids and mixtures thereof. By the term "adherent hydrocarbons" is intended herein normally liquid hydrocarbons associated with the solid particles, in contrast to a carbonaceous deposit, such as coke, which is also present on the solid particles. The relatively cold solids (e.g., cold coke) stream which is removed from the coking reactor for reheating in a heating zone is usually stripped with steam in the lower portion of the coking reactor to remove at least a portion of the adherent hydrocarbons from the cold solids stream before the cold solids stream is passed to a heating zone. The steam is usually introduced into the bottom of the coking reactor. Nevertheless, the cold solids stream removed from the coking reactor still comprises a significant amount of adherent hydrocarbons. When a stream of cold solids having a carbonaceous deposit (e.g., coke) and adherent hydrocarbons is passed to a heating zone such as a burner, to heat the solids, the adherent hydrocarbons are burned and, hence, not recoverable as liquids. A method that would improve the stripping of hydrocarbons from the cold solids stream would, therfore, be desirable since it would enable recovery of the adherent hydrocarbons and, hence, increase the yield of normally liquid hydrocarbons obtainable from the fluid coking process. By "normally liquid", with reference to hydrocarbons, is intended herein hydrocarbons that would be liquid at standard conditions.
U.S. Pat. No. 2,927,073 discloses introducing a stripping gas into the stripping section of a coking reactor as a plurality of streams.
It has now been found that by introducing the stripping gas as a plurality of streams into the stripping portion of the coker to provide a specified superficial velocity in the stripping section, the removal of adherent hydrocarbons from the cold solids will be increased.